A radiation imaging apparatus includes, for example, a pixel array in which a plurality of pixels are arrayed to form a plurality of rows and a plurality of columns, and a readout unit for reading out a pixel signal from each pixel. In the pixel array, for example, a plurality of column lines respectively corresponding to the plurality of columns are arranged, and pixels on each column are connected to a corresponding column line. For example, each pixel includes a detecting element for detecting radiation, and a switch for connecting the detecting element and the corresponding column line. If the switch is turned on, a signal corresponding to an irradiation amount is transferred from the detecting element to the column line.
Some radiation imaging apparatuses monitor signals from pixels after radiation irradiation for the pixel array starts, and generate a control signal to end the radiation irradiation based on the monitoring result. This control is also called Auto Exposure Control (AEC). Japanese Patent Laid-Open No. 7-201490 describes a technique of performing AEC by reading out signals from some pixels in a predetermined cycle after the start of radiation irradiation. In addition, Japanese Patent Laid-Open No. 2010-75556 describes a technique of performing AEC by maintaining the switches of pixels on a given row in an ON state and monitoring the signals of the pixels after the start of radiation irradiation.
Even if the switch of a pixel is kept in an OFF state during radiation irradiation, a potential change of the pixel caused by emitted radiation (more specifically, a potential change caused by detection of radiation by the detecting element of the pixel) may propagate to the corresponding column line. Propagation of the potential change to the column line is caused by capacitance coupling between the pixel and the column line, which will be referred to as “crosstalk” hereinafter in this specification.
In the methods described in Japanese Patent Laid-Open Nos. 7-201490 and 2010-75556, a signal read out via a column line includes a signal component from a pixel as a readout target and crosstalk components from the remaining pixels as non-readout targets. Especially, the crosstalk components have a larger value as the number of pixels increases, thereby decreasing the S/N ratio. This may decrease the accuracy of AEC.